Correct BNC Connector for AIS Antanna

[Andrew_Trayfoot]

Can anyone point me at the correct BNC plug for my GPS antenna.

 

[Alicatt]

That is a PL259 not a BNC, the PL259 mates with a SO239 socket.

 

[Andrew_Trayfoot]

No it's definitely a BNC.
I need to know the correct impedence for a GPS antenna.

 

[st599]

No it's definitely a BNC.
I need to know the correct impedence for a GPS antenna.

View attachment 169051

It's not a Bayonet NC, there's no bayonet fitting. Could be a TNC or similar.

It could be 75 ohm or 50 ohm, without the pin dimensions or cable marking it's hard to tell.

77 ohms is the lowest attenuation possible in co-ax, 30 is the maximum power transfer. So 75 is usually used for low loss reception, and 50 (a compromise value) used for transmission. But that's never guaranteed.

 

[awol]

Looks like a TNC - try Amphenol as a manufacturer.

 

[B27]

Yes, looks like TNC.
But check the size there are bigger and smaller connectors which look similar and your photo has no scale.
You needs to get the correct plug to suit the cable size and impedance, quite possibly the cable type such as 'RGnnn' might be printed along the cable. Otherwise a plug which suits the outer cable diameter will usually be OK.

 

[Alicatt]

yes, looks like a TNC connector
now what is the socket on the AIS device and what is the cable type as said above it will likely be some form of RGxx?

The GPS antenna connection on my radio is a SMA


There are lots of options to adapt to other sockets and plugs here
Amazon.co.uk : tnc adaptor

 

[wonkywinch]

The title of your thread says "Correct BNC Connector for AIS Antanna" but your post says "Can anyone point me at the correct BNC plug for my GPS antenna".

They work on completely different frequencies and the connectors differ for this reason. Boats (inc my own) seem to have whatever is handy at the time used which is not always correct. Which one do you need? AIS or GPS?

AIS = VHF = BNC, or N Type (B&G use PL/S259s)
GPS = UHF = SMA

 

[Plum]

The title of your thread says "Correct BNC Connector for AIS Antanna" but your post says "Can anyone point me at the correct BNC plug for my GPS antenna".

They work on completely different frequencies and the connectors differ for this reason. Boats (inc my own) seem to have whatever is handy at the time used which is not always correct. Which one do you need? AIS or GPS?

AIS = VHF = BNC, or N Type (B&G use PL/S259s)
GPS = UHF = SMA

Both my GPS and AIS devices came with BNC connectors for the aerial inputs. Is the BNC the only one that can be used for either?

 

[Andrew_Trayfoot]

OK to clarify this is a coax plug on the end of the cable for the gps antenna on my matsutec ais transponder.
Will post a photo of the back of the unit later....

 

[wonkywinch]

Both my GPS and AIS devices came with BNC connectors for the aerial inputs. Is the BNC the only one that can be used for either?

My guess is you'll have to use the opposite sex of whatever the manufacturer chose to fit on the device. Fitting adaptors is a waste of money. Generally BNC connectors are only used up to about 500MHz. GPS signals are around 1,200-1,600MHz.

Guide to RF Coaxial Connectors and Cables - AR RF/Microwave Instrumentation - AR Modular RF - Sunar RF Motion - AR Europe - WP

 

[Metalicmike]

There are so many different connections, i have reluctantly concluded that its easier to take it to a suitable retailer as I have bought the wrong one twice

 

[john_morris_uk]

My guess is you'll have to use the opposite sex of whatever the manufacturer chose to fit on the device. Fitting adaptors is a waste of money. Generally BNC connectors are only used up to about 500MHz. GPS signals are around 1,200-1,60MHz.

Guide to RF Coaxial Connectors and Cables - AR RF/Microwave Instrumentation - AR Modular RF - Sunar RF Motion - AR Europe - WP

I think you mean GPS are around 1.6 GHz (ie no 1600 Mhz). Some use 1.2 GHz as well.

 

[wonkywinch]

There are so many different connections, i have reluctantly concluded that its easier to take it to a suitable retailer as I have bought the wrong one twice

Getting confused now, are you Metalicmike or Andrew Trayfoot?

 

[jamie N]

I don't recommend it, but I've transmitted high quality colour video from an ROV by croc-clips; connecting a paper clip from the coax centre to the BNC panel centre, the screen sellotaped to the outer on the panel.
When needs must etc.etc..., but I'd always go with what the manufacturer has already, which is what the OP desired.
As an aside, until today I'd always believed that it was the British Naval Connector, and had never realised that there were credible alternatives in Bayonet Nut Connector or Bayonet Neill Concelman.

 

[john_morris_uk]

It's not a Bayonet NC, there's no bayonet fitting. Could be a TNC or similar.

It could be 75 ohm or 50 ohm, without the pin dimensions or cable marking it's hard to tell.

77 ohms is the lowest attenuation possible in co-ax, 30 is the maximum power transfer. So 75 is usually used for low loss reception, and 50 (a compromise value) used for transmission. But that's never guaranteed.

Your first two sentences are accurate.

Your final paragraph is… (can’t think of a polite word).

Rather than me going into explanation of how power handling is actually frequency dependant and then also depends on the conductor etc.

WATTS Power Handling for Coaxial Cables and Amplifiers

(It’s a few years since I was a scientific officer at what wax the Roysl Radar Establishment but I think I remember some things…)

 

[wonkywinch]

I think you mean GPS are around 1.6 GHz (ie no 1600 Mhz). Some use 1.2 GHz as well.

I missed a zero at the end of my 1,600MHz which I've corrected but am amazed at the pedantry of this forum .. Ofcom seem to think 1,600MHz is an accepted value for your 1.6 gigs

 

[john_morris_uk]

I missed a zero at the end of my 1,600MHz which I've corrected but am amazed at the pedantry of this forum .. Ofcom seem to think 1,600MHz is an accepted value for your 1.6 gigs

View attachment 169078

Not intended to be a pedant; just trying to be helpful.

 

[Andrew_Trayfoot]

Flippen heck, this is getting complicated!

This plug:


goes on the end of the the coaxial cable from the gps antenna of this:






Here:



I had to cut it off to get it through a bulkhead and the deck and hatch garage to my instrument panel.

I've had the instrument for a few years with the gps antenna fixed above the panel, but something has made it interfere with my Garmen GPS126. Moving the antenna soles the issue.


So I need to know what the right plug is to re do it...


Thanks
A.

 

[Andrew_Trayfoot]

Getting confused now, are you Metalicmike or Andrew Trayfoot?

I'm me....
Not sure who Metalicmike is.